Put meat in a saucepan with 2 liters of cold water and bring to the boil under a high heat. Peel a celeriac, 1 onion and 1 carrot. Reduce heat. Skim off the foam that rises to the surface, put the vegetables and cook for 1 hour and 30 minutes. Strain off the sauerkraut, cut into 1,5-2 cm long pieces. Warm up half the butter in the saucepan, put cabbage together with 1 tbsp. tomato paste, sprinkle with caraway seeds and simmer under the lid for 30 minutes. Peel and finely chop the remaining onion and carrots. Warm up the vegetable oil in a frying pan, put the vegetables, sprinkle with black pepper, fennel seeds and fry for 5-7 min. Add the remaining tomato paste and cook for another 4 minutes. Remove from fire. Peel potatoes and cut into cubes. Wash greens and grind. Peel garlic and crush. Take meat out of the broth and cut into small pieces. Strain out the broth and pour into a clean pan. Bring to the boil. Warm up the remaining butter in a frying pan and, stirring, fry the flour for 3 minutes until golden brown. Put the sliced meat and potatoes in the broth and cook for 10 minutes. Add the onion-and-carrot dressing, stewed cabbage, roasted flour, garlic, bay leaf and pepper. Bring back to boil and cook for 6 minutes. If necessary, salt the soup to taste. Put the greens, remove from fire, cover and let it brew for 30 minutes.